Reflex klystron of the double-disc type



K. L. TORSTENSSON ET AL 2,911,559 REFLEX KLYSTRON OF THE DOUBLE-DISC TYPE Filed Apri1 29, 1954 By MY. 54w;

United States Patent disc REFLEX KLYSTRON OF THE DOUBLE-DISC TYPE Karl Lennart Torstensson, Enskede, and Olof Martin Trawn, Bromma, Sweden, assignors to Telefonaktiebolaget L M Ericsson, Stockholm, Sweden, a corporation of Sweden Application April 29, 1954, Serial No. 426,376 Claims priority, application Sweden May 5, 1953 2 Claims. (Cl. 315-519) The present invention relates to a reflex klystron of the double-disc type.

In klystrons as heretofore known, an electron beam precise alignment and is centered in a fixed position rela-' central opening covered by a grid 13. The second plate tive to other parts within the tube envelope. Various means to obtain such mounting have been suggested, but the known means are not entirely satisfactory. The invention relates to an improved mOunting means'involving a number of advantages, further described in the following, which can not be obtained with the means as heretofore known.

The means according to the invention for centering the electron-gun when assembling vacuum tubes for which an exact alignment of the electrode system is required, e.g. reflex klystrons of the double-disc type,'is principally characterized by the cathode, the focusing system and the anode forming part of the electron-gun of the tube, being mounted on a holder, e.g. a tube base. The electron-gun is inserted until contacting a metal part, e.g. a klystron disc, designed in a corresponding manner and already sealed in the glass envelope of the tube, whereby alignment and centering are attained. The gun is fastened to said metal part by a solder, applied in suitable manner, whereby mechanical strength and electrical connection are assured.

' In order exactly to define the gap, formed between the plates (discs) in the tube, it is advantageous that the grid of the disc located nearest the glass base be'fasten'ed to the electron-gun unit before said unit is inserted into the tube. The adjustment of the said gap after the electron-gun unit has been inserted into the tube is then made by measuring the deviation of the resonance frequency from the desired nominal value and, guided thereby, said gap is thereafter adjusted by means of a tool, which is inserted through a hole, formed in the lower disc for the lower grid, whereupon the electron-gun is again inserted and fastened by soldering.

A vacuum tube, suitable for production by means of the above described arrangement according to the invention, and comprising an electron-gun unit with a cathode, an anode and a focusing electrode, two discs provided with central grids and forming part of a cavity resonator and also a reflector electrode, is principally characterized' by providing the disc, located nearest the tube-base, with a sleeve-shaped part and by shaping the anode, forming part of the electron-gun unit, like a sleeve and arranging the same for insertion into said part. The disc and the anode are suitably of a conical shape, particuwith a cylindrical sleeve or collar.

The invention will be further described in the following in connection with an embodiment of a double-disc klystron, shown on the single figure of the drawing.

On the drawing there are shown the electron-gun and a unit comprising the tube envelope 1 and the discs 2, 3 for a reflex klystron before the former has been inserted into the latter unit when assembling the tube. The electron-gun comprises a glass base 10 provided with terminals 11 leading'tothe electrodes forming part of the electron-gun. These electrodes are a cathode 6, a focusing electrode 8, concentric with said cathode and provided with a grid 16, and an anode 9, concentric with said two electrodes. The cathode 6, the focusing elec trode 8 and the anode 9 are fastened to a ceramic disc 7. The anode forms at the top a cylinder 14 and below said cylinder a truncated cone. The said cylindrical shaped part of the embodiment shown is at the top covered by a grid 12. When assembling the tube the electron-gun must be inserted into the unit shown above the electron-gun on the drawing. This unit comprises the glass envelope 1 of the klystron with a reflector 4 sealed in said bulb. The plate or disc 2 is sealed in the glass envelope below the reflector 4 and is provided with a or disc 3 is sealed in the envelope below the disc 2 and provided with [an inner conductor 5, shaped like a truncated cone, provided with a cylindrical collar 15 at the top, whereby an orifice corresponding to an orifice in the disc 2 is defined by the collar 15 in the plate 3. The said plates or discs 2 and 3 form a part of the cavity resonator which'is to cooperate with the tube. The grid 12 on the anode 9 has to close in an assembled tube the central opening in the plate 3, whereby the distance between the two grids 13 and 12 forms the gap of the cavity resonator, through which the beam emanating from the electron-gun has to pass to experience velocity modulation. For vacuum tubes of this kind it is imperative, that said distance or gap between the two grids 12 and 13 is determined with regard to the desired frequency range, and that the difierent electrodes are exactly centered relative to one another. i

When assembling the electron-gun and the tube unit containing the discs, the former is moved toward the disc 3 until it touches the same, the parts 15 and 5 of said disc 3 and the part 14 and the conical part of the anode 9 being formed in a corresponding manner so that they nest one into another. The electron-gun will thereby be centered relative to the disc 3, which in its turn has been centered relative to the disc 2 and the reflector anode 4 already during the sealing process. The different electrodes forming part of the electron-gun are easy to center during the assembly of this gun. The distance between the grid 12, fastened to the anode, and the grid 13, fastened to the disc 2 is fixed by pressing against each other the parts of the anode 9 and the disc 3, which are formed in a corresponding manner. By applying solder and heat, e.g. in the space between the collarshaped part 15 and the cylinder 14, the electron-gun and the lower disc 3 are thereafter soldered together, whereby the necessary mechanical strength and electric connection are secured. The base 10 and the glass envelope 1 are firmly fused and evacuated in a customary manner.

The adjustment of the grids is suitably made in such a Way that after inserting the electron-gun unit until it rests with its corresponding parts against the lower disc 3, the resonance frequency is measured for the cavity resonator in which the gap, formed between the discs 2 and 3, is included. After removing again the electron-gun unit, the distance between these discs, guided by the measured and the desired value of said resonance frequency,

Patented Nov. 3, 1.959v

is adjusted by means of a suitable tool inserted from outside through the central hole in the disc 3. The electron-gun is then again inserted and fastened by soldering in the manner described above. a

A very exact control and adjustment of the diflerent electrode distances can in a simple way be obtained by means of the procedure according to the invention. A separate mounting of the electron-gun unit itself will thus enable control and adjustment, step by step, of the electrode distances in said unit, e.g. the cathode-grid distance (616), the cathode-anode distance (69). According to heretofore known methods of producing reflex klystrons of the kind described, the distances between the grids .in the discs 2 and 3 have been adjusted when the discs were sealed in the tube envelope 1. The invention permits an adjustment of said distance quite independent of the fixing of the discs and, moreover, a control measurement and after-adjustment of said distance are also made possible before the tube base and envelope are tightly fused together without aflecting the abovementioned gap.

By forming the anode and the lower disc so that they correspond to each other, the centering of the electrodes will also be accurate and the position is fixed by parts of the anode pressing against the inner conductor 5 and the collar of the lower disc 3.

When one resonator-grid, to wit grid 12, is mounted on the electron-gun unit, an effective cleaning of the space between the two klystron discs 2 and 3 is readily possible, which is of great importance in manufacturing of tubes.

The fact that the electron-gun has been shown in mounted position on the tube base 10 according to the drawing, does not imply that the high anode voltage should necessarily be connected to the pins of the tube base, which sometimes may be disadvantageous, since the anode voltage may be supplied through the resonator as well.

The invention has been described above in connection with reflex klystrons, but it is also applicable for the production of other vacuum tubes, in which equivalent problems in regard to centering'and alignment of the electrodes are present.

We claim:

1. A reflex klystron of the double-disc type, comprising, in combination, -a self-contained electron-gun assembly including an insulation base, a cathode supported on said base, a focusing electrode enveloping said cathode coaxially therewith and supported on the base, a grid supported by said focusing electrode in front of the cathode, an anode enveloping said focusing electrode coaxially therewith and supported on the base, said anode having a frusto-conical part and an open ended cylindrical part protruding from. the narrow end of said frusto-conical part, and a resonator grid fitted in said cylindrical part; and a self-contained resonator assembly including an envelope closed at one end and open at the other end, a

first apertured disc peripherally sealed to said envelope, a reflector mounted within said envelope between the closed envelope end and said first disc in registry with the aperture of the latter, a second disc peripherally sealed to the envelope on the opposite side of said first disc, said second disc having a frusto-conical center part and an open ended cylindrical part protruding from the narrow end of the frusto-conical part, said frusto-conical and cylindrical parts of the anode and the second disc matching each other, said gun assembly extending into the open end of said envelope with the frusto-conical part and the cylindrical part of the anode nested in the frustoconical part and the cylindrical part respectively of the second disc in abutting relationship; and means fixedly securing the abutting surfaces of the frusto-conical and cylindrical parts to each other.

2. A reflex klystron of the double-disc type, comprising, in combination, a self-contained electron-gun assembly including an insulation base, a cathode supported on said base, a focusing electrode enveloping said cathode co axially therewith and supported on the base, an anode enveloping said focusing electrode coaxially therewith and supported on the base, said anode having a frustoconical part and an open ended cylindrical part protruding from the narrow end of said frusto-conical part, and a resonator grid fitted in said cylindrical part; and a selfcontained resonator assembly including an envelope closed at one end and open at the other end, a first apertured disc peripherallysealed to said envelope, a reflector mounted within said envelope between the closed envelope end and said first disc in registry with the aperture of the latter, a second disc peripherally sealed to the envelope on the opposite side of said first disc, said secondv disc having a frusto-conical center part and an open ended cylindrical partprotruding from the narrow end of the frusto-conical part, said frusto-conical and cylindrical parts of the anode and the second disc matching each other, said gun assembly extending into the open end of said envelope with the frusto-conical part and the cylindrical part respectively of the second disc in abutting relationship; and means fixedly securing the abutting surfaces of the frusto-conical and cylindrical parts to each other.

References Cited in the file of this patent UNITED STATES PATENTS 2,174,853 Bowie Oct. 3, 1939 2,411,184 Beggs Nov. 19, 1946 2,489,156 Rigrod Nov. 22, 1949 2,567,674 Linder Sept. 11, 1951 2,581,408 Hamilton Jan. 8, 1952 2,605,442 ONeill July 29, 1952 2,605,444 Garbuny July 29, 1952 2,629,066 Eitel et al. Feb. 17, 1953 2,680,209 Veronda June 1, 1954 2,809,322 Hernqvist Oct. 8, 1957 

